Add DataShare utility class for Mbed-OS applications

/**

 *

 * Built with ARM Mbed-OS

 *

 * Copyright (c) 2019-2021 Embedded Planet, Inc.

 * SPDX-License-Identifier: Apache-2.0

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#if MCUBOOT_DATA_SHARING && !MCUBOOT_BOOTLOADER_BUILD

#include "DataShare.h"

#include "boot_status.h"

#include <cstring>

#define PTR_TO_UINT8(x) ((volatile uint8_t *) x)

#define PTR_TO_UINT16(x) ((volatile uint16_t *) x)

#define PTR_TO_UINT32(x) ((volatile uint32_t *) x)

#define SHARED_DATA_ENTRY_BASE MCUBOOT_SHARED_DATA_BASE+SHARED_DATA_HEADER_SIZE

DataShare::DataShare(uint8_t *shared_base) : _shared_base(shared_base) {

    volatile uint16_t *ptr = PTR_TO_UINT16(MCUBOOT_SHARED_DATA_BASE);

    /* Validate magic word */

    if(*ptr++ == SHARED_DATA_TLV_INFO_MAGIC) {

        _is_valid = true;

    }

    _total_size = *ptr;

}

bool DataShare::is_valid() {

    return _is_valid;

}

uint16_t DataShare::get_total_size() {

    if(!is_valid()) {

        return 0;

    }

    return _total_size;

}

int DataShare::get_next(uint16_t *type, mbed::Span<uint8_t> buf, uint16_t *actual_size) {

    if(!is_valid()) {

        return DATA_SHARE_ERROR_CORRUPT;

    }

    if(_current_offset >= (_total_size - SHARED_DATA_HEADER_SIZE)) {

        return DATA_SHARE_ERROR_EOF;

    }

    uint16_t working_offset = _current_offset;

    /* Get the type and the length */

    *type = *PTR_TO_UINT16((SHARED_DATA_ENTRY_BASE + working_offset));

    working_offset += sizeof(uint16_t);

    *actual_size = *PTR_TO_UINT16((SHARED_DATA_ENTRY_BASE + working_offset));

    working_offset += sizeof(uint16_t);

    /* Check if the output buffer is large enough */

    if((size_t)buf.size() < *actual_size) {

        return DATA_SHARE_ERROR_OUT_OF_MEM;

    }

    /* Copy data of TLV entry */

    memcpy(buf.data(), (const uint8_t*)PTR_TO_UINT8((SHARED_DATA_ENTRY_BASE + working_offset)), *actual_size);

    working_offset += *actual_size;

    /* Update state */

    _current_offset = working_offset;

    return DATA_SHARE_OK;

}

void DataShare::rewind() {

    _current_offset = 0;

}

#endif /* MCUBOOT_DATA_SHARING && !MCUBOOT_BOOTLOADER_BUILD */

/**

 *

 * Built with ARM Mbed-OS

 *

 * Copyright (c) 2019-2021 Embedded Planet, Inc.

 * SPDX-License-Identifier: Apache-2.0

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#ifndef DATASHARE_H_

#define DATASHARE_H_

/**

 * This is an utility intended to be used by the booted application rather

 * than by the bootloader

 */

#if MCUBOOT_DATA_SHARING && !MCUBOOT_BOOTLOADER_BUILD

#include <stdint.h>

#include "platform/Span.h"

/* Error codes */

#define DATA_SHARE_OK               0

#define DATA_SHARE_ERROR_EOF        1   /* No more TLV entries available */

#define DATA_SHARE_ERROR_OUT_OF_MEM 2   /* The output buffer was not large enough to hold the contents of the TLV entry */

#define DATA_SHARE_ERROR_CORRUPT    3   /* Data corruption has been detected */

/**

 * Class enabling iterator-style access to the TLV-encoded data shared

 * by an mcuboot-based bootloader.

 */

class DataShare

{

public:

    /**

     * Initializes a DataShare iterator at the given base address

     * @note the configured MCUBOOT_SHARED_DATA_BASE address is used by default

     */

    DataShare(uint8_t * shared_base = ((uint8_t *) MCUBOOT_SHARED_DATA_BASE));

    /**

     * Validates the magic number of the shared data section

     * @return true if magic number is found, false otherwise

     */

    bool is_valid();

    /**

     * Gets the total size of the shared data region

     * @return 0 if shared data region is not valid, otherwise the size of the shared data region

     */

    uint16_t get_total_size();

    /**

     * Attempts to get the next TLV entry in the shared data memory

     * @param[put] type Type code of the data entry

     * @param[out] out Output buffer span

     * @param[out] actual_size Size of entry copied to output buffer in bytes

     * @return err Zero if output buffer contents is valid (successful), non-zero on failure

     */

    int get_next(uint16_t *type, mbed::Span<uint8_t> buf, uint16_t *actual_size);

    /**

     * Resets the iterator-like pointer to the first TLV element in the shared

     * data region

     */

    void rewind();

protected:

    uint8_t *_shared_base;

    bool _is_valid = false;

    uint16_t _total_size = 0;

    uint16_t _current_offset = 0;

};

#endif /* MCUBOOT_DATA_SHARING && !MCUBOOT_BOOTLOADER_BUILD */

#endif /* DATASHARE_H_ */